Molybdenum disulfide laminar flow film and preparation method and application thereof

Abstract

The invention relates to the technical field of separation membrane materials, in particular to a molybdenum disulfide laminar flow membrane and a preparation method and application thereof.The preparation method comprises the following steps that molybdenum disulfide nanosheets are added into pure water, metal salt is added after the molybdenum disulfide nanosheets are dissolved, and a molybdenum disulfide solution is obtained; adding potassium hydroxide into pure water to prepare a potassium hydroxide solution; adding sodium hydrogen sulfite into pure water to prepare a sodium hydrogen sulfite solution; cleaning the ultrafiltration membrane with pure water, soaking the ultrafiltration membrane in a potassium hydroxide solution, taking out the ultrafiltration membrane after a first time, cleaning the ultrafiltration membrane for the second time with pure water, then transferring the ultrafiltration membrane into a sodium hydrogen sulfite solution for soaking, taking out the ultrafiltration membrane after a second time, cleaning the ultrafiltration membrane for the third time, and soaking the ultrafiltration membrane in pure water for later use; and loading the obtained molybdenum disulfide solution to the surface of an ultrafiltration membrane obtained after third cleaning through a vacuum filtration technology to obtain the molybdenum disulfide laminar flow membrane. The molybdenum disulfide laminar flow membrane has the advantages of low water mass transfer resistance and high water flux, and can realize efficient removal of heavy metals Pb < 2 + >, Hg < 2 + > and UO2 < 2 + >.

Description

Technical Field

[0001] The invention relates to the technical field of separation membrane materials, and in particular to a molybdenum disulfide laminar membrane and a preparation method and application thereof. Background Art

[0002] Toxic heavy metal ions such as mercury (Hg) and lead (Pb) and radionuclides such as uranium (U) in water pose a serious threat to human and animal health. They can accumulate through the food chain and pose risks to human health, such as severe liver damage or cancer. Therefore, it is of great significance to develop effective treatment technologies for trace amounts of toxic heavy metals or radionuclides.

[0003] In the past few decades, various methods for removing heavy metals and nuclides from water have been developed and evaluated, such as membrane filtration, adsorption, and chemical precipitation. Adsorption technology has attracted attention due to its advantages such as simple operation and easy availability of materials. However, the application of high specific surface area nano-adsorbent materials is limited by their disadvantages such as difficulty in recovery and easy saturation. Membrane technology has the advantages of simple operation, high cost-effectiveness, and stable removal performance, but it also has the "trade-off" effect that it is difficult to improve permeability and selectivity at the same time.

[0004] Two-dimensional transition metal dichalcogenides (TMDCs) are a class of layered materials that are connected by covalent bonds within the plane and interact with each other by van der Waals forces. As a member of the TMDCs family, MoS2 nanomaterials are rich in sulfur ions (S 2- ), in the presence of competing ions, it has a high and strong selective adsorption capacity for soft acid metals such as Hg and Pb. However, the free spacing between adjacent layers is small (0.3nm), which limits the ions from entering the interior and reacting with S 2- contact. Therefore, it is necessary to increase the interlayer spacing of MoS2 to efficiently remove pollutants such as heavy metals and radionuclides; at the same time, expand the two-dimensional channels between MoS2 sheets to increase the water flux of the laminar membrane. Unlike graphene oxide, which contains a large number of oxygen-containing active sites, the sulfur layer on the surface of MoS2 is chemically inert and difficult to chemically modify. How to prepare a new two-dimensional material modified membrane with high permeability and retention performance is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The object of the present invention is to provide a molybdenum disulfide laminar membrane and a preparation method and application thereof, which can solve the above-mentioned technical problems.

[0006] The present invention provides a method for preparing a molybdenum disulfide laminar film, comprising the following steps:

[0007] Step 1: Add molybdenum disulfide nanosheets to pure water, add metal salt after ultrasonic dissolution, and continue ultrasonication to obtain a molybdenum disulfide solution (i.e., a mixed solution of molybdenum disulfide and metal salt), which is referred to as molybdenum disulfide solution for convenience of expression;

[0008] Step 2: Add potassium hydroxide (KOH) to pure water, stir and dissolve it to obtain a potassium hydroxide solution;

[0009] Step 3: Add sodium bisulfite (NaHSO3) to pure water, stir and dissolve it to obtain a sodium bisulfite solution;

[0010] Step 4: After washing the ultrafiltration membrane with pure water, immerse it in the potassium hydroxide solution obtained in step 2, take it out after the first time and wash it with pure water for the second time, then transfer it to the sodium bisulfite solution obtained in step 3 and soak it, take it out after the second time, wash it for the third time, and then soak it in pure water for standby use;

[0011] Step 5: The molybdenum disulfide solution obtained in step 1 is loaded onto the surface of the ultrafiltration membrane obtained in step 4 (i.e., the ultrafiltration membrane obtained after the third washing) by vacuum filtration technology to obtain a molybdenum disulfide laminar membrane.

[0012] The order of the above steps 1-3 is not particularly limited, and the solutions can be prepared simultaneously or separately.

[0013] Preferably, the added amount of the molybdenum disulfide nanosheets is 1 mg / L-5 mg / L, that is, 1-5 mg of molybdenum disulfide nanosheets are added per liter of pure water.

[0014] Preferably, the metal salt is one of sodium chloride (NaCl), magnesium chloride (MgCl2), calcium chloride (CaCl2), cupric chloride (CuCl2), ferrous chloride (FeCl2), and aluminum chloride (AlCl3).

[0015] Preferably, the added amount of the metal salt is 0.001 mol / L-0.1 mol / L, that is, 0.001-0.1 mol of the metal salt is added per liter of pure water.

[0016] Preferably, the concentration of the potassium hydroxide solution obtained in step 2 is 0.05 mol / L, and the concentration of the sodium bisulfite solution obtained in step 3 is 0.05 mol / L.

[0017] Preferably, in step 1, after molybdenum disulfide is added to water and metal salt is further added, ultrasonic treatment is performed for 20-30 minutes to complete the dissolution process and the fusion of metal cations.

[0018] Preferably, the type of the ultrafiltration membrane is one of polysulfone (PS), polyethersulfone (PES) or polyvinylidene fluoride (PVDF) membrane, which needs to be soaked in KOH solution for 5-15 minutes (first time) and soaked in NaHSO3 solution for 5-15 minutes (second time) to complete the surface activation process.

[0019] The invention also provides a molybdenum disulfide laminar membrane, which is prepared according to the above preparation method.

[0020] The present invention also provides an application of the molybdenum disulfide laminar membrane in removing heavy metals, radionuclides and organic matter in water.

[0021] Beneficial effects of the present invention:

[0022] In the preparation process of the present invention, the monolayer of molybdenum disulfide nanosheets is orderly reorganized, and the two-dimensional channels are expanded by intercalation of metal cations with different hydration radii to obtain laminar membranes with different interlayer spacings, coupled with adsorption and size exclusion, to remove heavy metals and radioactive nuclide ions in water in a targeted and efficient manner. After the metal cations are intercalated into the nanosheets, the interlayer spacing of the nanosheets is further expanded to form a two-dimensional nanochannel that facilitates water flow, effectively improving the water flux, and the effective interlayer spacing can intercept UO2 in the water through the size exclusion effect. 2+ In addition, MoS2 provides S 2- Soft acid heavy metals and some UO2 can be removed through Lewis soft-soft interaction 2+ The prepared metal cation intercalated MoS2 laminar membrane has the advantages of low water mass transfer resistance and high water flux. The synergistic effect of coupled size screening and adsorption can achieve heavy metal Pb 2+ , Hg 2+ and UO2 2+ Efficient removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the process of loading the molybdenum disulfide solution onto the surface of the ultrafiltration membrane by vacuum filtration technology in the method for preparing the molybdenum disulfide laminar membrane of the present invention;

[0025] Figure 2 The top surface and cross-section scanning electron microscope (SEM) morphology images of the M, M-Na, M-Mg, and M-Al films in the embodiments of the present invention and the comparative examples are shown. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a molybdenum disulfide laminar film comprises the following steps:

[0031] (1) Add 3 mg of molybdenum disulfide nanosheets to 1 L of pure water, add 0.1 mol of NaCl and ultrasonicate for 30 min to prepare a sodium ion-fused molybdenum disulfide solution;

[0032] (2) Add KOH to pure water and stir until fully dissolved to prepare a 0.05 mol / L KOH solution;

[0033] (3) Add NaHSO3 to pure water and stir until fully dissolved to prepare a 0.05 mol / L NaHSO3 solution;

[0034] (4) After washing the PVDF membrane with pure water, immerse it in the KOH solution prepared in step (2) for 15 minutes, take it out and wash it with pure water for a second time, then transfer it to the NaHSO3 solution prepared in step (3), immerse it for 15 minutes, take it out and wash it with pure water for a third time, and rinse with pure water to remove excess solution on the surface;

[0035] (5) The solution prepared in step (1) is loaded onto the surface of the ultrafiltration membrane obtained in step 4 by vacuum filtration technology. After vacuum filtration, a metal cation intercalated molybdenum disulfide laminar membrane is prepared and recorded as M-Na membrane. The upper surface and cross-section scanning electron microscopy SEM morphology are as follows: Figure 2 As shown in (b, f).

[0036] Metal cation intercalated MoS2 laminar membrane can be used to remove heavy metal ions and trace radioactive nuclides uranyl ions (UO2 2+ ), in order to examine the performance of the laminar membrane, the prepared laminar membrane was placed in a cross-flow membrane filtration system for testing, and the pure water flux and the removal rate of heavy metals and radionuclides of the laminar membrane were examined. Specifically, the prepared laminar membrane was placed in a cross-flow filtration system for filtration experiments under a pressure of 2 bar, and 0.5 mg / L of Pb 2+ , Hg 2+ As influent, test the heavy metal retention performance of laminar flow membrane; take 0.5mg / L UO2 2+ The radionuclide retention performance of the laminar flow membrane was determined through filtration experiments using the influent as feed water. 1 mg / L tetracycline was selected as an organic pollutant to carry out separation experiments and test the organic matter separation effect of the laminar flow membrane.

[0037] Example 2

[0038] Based on the modification method in Example 1, the only difference is that the metal salt added in step (1) is MgCl2. The obtained laminar membrane is denoted as M-Mg. The SEM morphology of its upper surface and cross-section is as follows: Figure 2 As shown in (c, g).

[0039] Example 3

[0040] Based on the modification method in Example 1, the only difference is that the metal salt added in step (1) is AlCl3, and the obtained laminar membrane is denoted as M-Al. The SEM morphology of its upper surface and cross-section is as follows: Figure 2 As shown in (d, h).

[0041] Comparative Example

[0042] Based on the modification method in Example 1, the only difference is that no metal salt is added in step (1), and a laminar membrane (M membrane) is obtained, and then the separation performance of the membrane is tested. The top surface and cross-section scanning electron microscopy SEM morphology of the M membrane are as follows: Figure 2 As shown in (a, e).

[0043] The test data of the composite laminar membranes prepared in Examples 1-3 and Comparative Examples are shown in Table 1.

[0044] The detailed data comparison is as follows:

[0045] Table 1 Test data of laminar membrane in Examples 1-3 and Comparative Examples

[0046]

[0047] The top surface and cross-section scanning electron microscope (SEM) morphologies of the four laminar membranes in Examples 1-3 and Comparative Examples are shown in FIG. Figure 2 As shown. Compared with the comparative example, after the cations supported the nanochannels, the interlayer spacing of the laminar membrane increased significantly. It can be seen that the addition of metal cations has no obvious effect on the membrane surface morphology, but can form a stable interlayer structure supported by cations, which is beneficial to the improvement of membrane water flux.

[0048] The laminar membrane water flux in Examples 1-3 and Comparative Examples, heavy metal ions (Pb 2+ , Hg 2+ ), radionuclides (UO2 2 + ) and organic matter removal effects are shown in Table 1. Compared with the laminar membrane M without cation support, the water flux of the metal cation supported laminar membrane M-Na prepared in Examples 1-3 of the present invention was significantly increased by 1.73 times, 1.79 times, and 1.86 times, respectively, reaching 908 L / (m 2 ·h)、938L / (m 2 ·h)、973L / (m 2 h). The laminar membrane prepared by the present invention has a significant heavy metal ion interception capacity, Pb 2+ , Hg 2+ The interception rate is between 86.5% and 96.4%; radionuclide UO2 2+ The interception rates are all above 98%. In addition, the tetracycline interception rate of the laminar membrane can be maintained above 98%. In summary, the metal cation-supported molybdenum disulfide laminar membrane prepared by the present invention has high water flux, excellent removal effect of heavy metal ions and radionuclides, and good removal effect of organic matter, which provides a new idea for the performance optimization of laminar membranes.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a molybdenum disulfide laminar membrane, characterized in that The following steps are involved: Step 1: Add molybdenum disulfide nanosheets to pure water, dissolve them by ultrasonication, then add metal salt, and continue ultrasonication to obtain a molybdenum disulfide solution; Step 2: Add potassium hydroxide to pure water, stir to dissolve it, and obtain a potassium hydroxide solution; Step 3: Add sodium bisulfite to pure water, stir to dissolve it, and obtain a sodium bisulfite solution; Step 4: After washing the ultrafiltration membrane with pure water, immerse it in the potassium hydroxide solution obtained in step 2, take it out after the first time and wash it with pure water for the second time, then transfer it to the sodium bisulfite solution obtained in step 3 and soak it, take it out after the second time, wash it with pure water for the third time, and then soak it in pure water for standby use; Step 5: The molybdenum disulfide solution obtained in step 1 is loaded onto the surface of the ultrafiltration membrane obtained in step 4 by vacuum filtration technology to obtain a molybdenum disulfide laminar membrane.

2. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: The added amount of the molybdenum disulfide nanosheets is 1 mg / L-5 mg / L.

3. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: The metal salt is one of sodium chloride, magnesium chloride, calcium chloride, cupric chloride, ferrous chloride and aluminum chloride.

4. The method for preparing a molybdenum disulfide laminar membrane according to claim 3, characterized in that: The added amount of the metal salt is 0.001 mol / L-0.1 mol / L.

5. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: The concentration of the potassium hydroxide solution obtained in step 2 is 0.05 mol / L, and the concentration of the sodium bisulfite solution obtained in step 3 is 0.05 mol / L.

6. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: In the step 1, the ultrasonic time for adding molybdenum disulfide to water and adding metal salt is 20-30 minutes.

7. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: The type of the ultrafiltration membrane is one of polysulfone, polyethersulfone or polyvinylidene fluoride membrane.

8. The method for preparing a molybdenum disulfide laminar membrane according to claim 1, characterized in that: The first time is 5-15 minutes, and the second time is 5-15 minutes.

9. A molybdenum disulfide laminar membrane, characterized in that: Prepared according to any one of the preparation methods of claims 1-8.

10. Use of the molybdenum disulfide laminar membrane according to claim 9 in removing heavy metals, radionuclides and organic matter in water.

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